Field of the Invention
The present invention relates generally to the field of apparatus for biological laboratory sample testing and more particularly to biological fluid specimen test tubes for use with such apparatus.
For numerous medical purposes, measurement of the rate at which a patient's blood coagulates or clots is necessary. One of these purposes relates, as an example, to kidney dialysis or blood cleansing treatments for patients having kidney problems. During subsequent treatments, and perhaps more than once in the course of a single treatment, measurement of the rate at which the patient's blood coagulates is essential to establishing or adjusting treatment parameters.
Typically, blood coagulation rate or the time required to reach a predetermined degree of coagulation is determined by subjecting a small specimen of the patient's blood to a coagulation test. In such a test, a vial or small test tube containing the blood specimen, together generally, with small quantities of selected additives such as siliceous Earth, is agitated in some manner while consistence of the blood in the specimen holder is monitored for coagulation.
Frequently, the monitoring is done automatically using a light source on one side of a transparent blood specimen holder and a light sensitive photo detector on an opposite side of the holder. As the blood specimen thickens and coagulates, its light transmitting characteristics are reduced. Thus, when light transmitted through the blood specimen, as detected by the photosensor, falls to a level corresponding to a preselected extent of coagulation as previously determined by suitable system calibration, the photosensor may be used to automatically trigger stop a timer, which was started when coagulation test started.
As can readily be appreciated, very precise and accurate coagulation rate determinations are often critical to a patient's life. A high degree of precision and accuracy is particularly necessary when monitoring for slight changes in a patient's blood coagulation rate as is often the situation.
Heretofore, the necessary precision and accuracy in determining blood specimen coagulation rate or time to coagulate has been difficult if not generally impossible to achieve, even when the tests have been performed with great care. To a large extent, this lack of precision and accuracy has been caused by the manner in which the blood specimen has been contained during the coagulation tests. Typically, small cylindrical test tubes of the type and configuration commonly used in chemical laboratories have been used to hold the blood specimen. As a result, when the tube is agitated, usually by rocking or tilting a horizontally oriented tube up and down so that the blood specimen runs back and forth between ends of the tube, the blood tends to "wash" around inside the tube in a sufficiently uncontrolled manner that transmission of coagulation selecting light is affected. Also, since the tube is round in cross section, light shining downwardly through the tube from an external source towards a photosensor tends to be diffused and reflected in a difficult to predict manner. Degree of translucency is a critical parameter for determining coagulation time.
As a result of blood specimen movement around the inside of the specimen holding tube, and depression and reflection of light from the light source as the tube is rocked to induce coagulation, erroneous light readings are often made by the photosensor. That is, at certain positions of the specimen tube and for certain uncontrolled movement of the blood, light reading of the photosensor may indicate the desired degree of coagulation has been reached when, in fact, such is not the case. Under other conditions, the light reading may indicate lack of coagulation after the desired degree of coagulation has already been reached.
Other problems have retarded the coagulation of the blood sample as it is introduced into the specimen holder, thereby possibly affecting coagulation rate, and difficulty in always filling the specimen holder to the same extent, or leakage of part of the specimen from the holder, thereby changing light transmission characteristics of the sample because of translucency variation.
Because of these and other problems with blood specimen holders for coagulation tests, applicant has invented a special specimen holder which overcomes many, if not all, of these problems.